SSD SRT caching question

I am about to buy my SSD, but I don't know whether I can use the Crucial M4 64GB for caching, next to using it for my complete OS and a game (maybe two, 7 GB average). Because what I would like to do, is put my OS on it (Win7 64-bit) and the game. And then use (a part of) the space left (around 30GB, reserving 27GB for the OS and 3~4GB for the game) for Caching.

Will this work? Or can I only use the Intel SSD Caching on a empty SSD?

P.S. Someone told me I could only use ~20GB or 60GB for SRT Caching, I find this hard to believe, is it true?
P.P.S. Is it true I ought to put the SRT Caching to 64GB? Or would there actually be a difference if I would put my OS and Call of Duty 4 directly on my SSD?

With Intel's SRT Technology you can use the SSD to cache your frequently used data via software. I just saw a video on youtube by Linus about SRT and it does look like it that you can only use 18GB or 60GB. Anyone know if the difference between putting a game completely on the SSD and using SRT caching is big?

Here's a description of SRT which makes a caveat on the usage (scroll to "How to set up ...")

In most cases, it’s not going to be possible to use Smart Response Technology without re-installing Windows on your PC, because you must activate RAID mode in the BIOS to enable SRT. We expect that most motherboards based on the Z68 chipset will be set to IDE or AHCI mode by default, like our Gigabyte Z68X-UD5-B3, so you must make sure you change this before installing Windows.